Omodeo on Azzolini, 'The Duke and the Stars: Astrology and Politics in Renaissance Milan'

Monica Azzolini
Pietro Daniel Omodeo

Monica Azzolini. The Duke and the Stars: Astrology and Politics in Renaissance Milan. I Tatti Studies in Italian Renaissance History Series. Cambridge: Harvard University Press, 2012. Illustrations. 370 pp. $49.95 (cloth), ISBN 978-0-674-06663-2.

Reviewed by Pietro Daniel Omodeo (Max Planck Institute for the History of Science) Published on H-PhysicalSciences (December, 2013) Commissioned by Marta Jordi Taltavull

Uses and Abuses of Astrology in Renaissance Milan

The intellectual relevance of astrology in the cultural and academic panorama of the late medieval and early modern periods is well known and has been widely treated in the history of science and ideas. In this respect, it should be sufficient to mention seminal works by Lynn Thorndike (A History of Magic and Experimental Science, 8 volumes [1923-58]), Eugenio Garin (Lo zodiaco della vita: La polemica sull’astrologia dal Trecento al Cinquecento [1976]), and Anthony Grafton (Cardano’s Cosmos: The Worlds and Works of a Renaissance Astrologer [1999]). Yet a wide and detailed treatment of astrological practices and the manner in which the “science of the stars” affected the lives of Renaissance people both in their everyday life and on a political scale was still a desideratum. Monica Azzolini contributes to fill this gap with a fresh and innovative investigation of astrological practice in the court of the Sforza dukes from the raise of their dynasty under Francesco, in 1450, to its fall when Milan capitulated to the French army, in 1499. Her study is based on a wide range of materials so far neglected by historians, in particular letters, manuscripts, and documents related to the Milanese Quattrocento preserved in Italian and European archives and libraries. Her detailed discussion of epistolary exchanges, interpretations of horoscopes, and medical reports demonstrates how important astrological expertise was in the eyes of the ruling classes of that age. These documents permit her not only to unveil the backstage of Renaissance diplomacy but also to scrutinize the passions, hopes, and fears of those prominent people, who confidentially asked their trusted astrologers remedies for health problems, analyses of uncertain political scenarios, support in their decisions, and confirmation of their expectations.

The book opens with a chapter summarizing the theoretical tenets of Renaissance astrology and, more particularly, reconstructing the teaching of astrology and astrological medicine at Pavia, which was the University of the Duchy, closely linked to the Milan court. The rest of the book is the narration of a family saga from the viewpoint of the patronage of astrology in the context of evolving Italian politics. Chapters 2 to 5 are devoted to one of the four succeeding Sforza dukes, whose different uses of astrology permit Azzolini to examine different aspects of that discipline and of its practice. Chapter 2 introduces the issues of astrological medicine at court, and the application of astrology to the planning of dynastic alliances during the reign of Francesco Sforza and Bianca Maria Visconti. In the case of marriage strategies, the nativities of the dukes’ progenies and of their fiancées were passed under close examination, to assess the compatibility of the candidate newlyweds, as well as their virtues, weaknesses, and even physical health. Chapter 3 deals with political astrology under Francesco’s successor, his son Galeazzo Maria, who was both a supporter of that practice and a victim of astrological rumors. His bloody murder, on December 26, 1476, was preceded and followed by “an extraordinary flourishing of astrological prognostications,” which might jeopardize his power and, after his death, explained and justified his fate by means of astrology (p. 127). Chapter 4 deepens the issue of medical astrology by considering the case of Galeazzo’s sickly son Gian Galeazzo, who nominally succeeded him at the young age of nine. For his immaturity and continuous illness, the new duke was excluded from power by his tutor and uncle Ludovico Maria who became the de facto ruler of Milan. While Gian Galeazzo was relegated to the Castle of Pavia, his health was the subject of an intense correspondence between physicians using astrological medicine and his relatives, in particular Ludovico. The doctors sent medical bulletins, reported about the duke’s reluctance to be cured, and resorted to astrology to account for his eventual death. Azzolini’s reconstruction offers a unique insight into intimate aspects of the lives of the Sforza family and the plots of Ludovico to gain power at the expense of his nephew. Her investigation has special relevance in the light of famous allegations directed against Ludovico. Contemporaries and historians accused him to be the murder of Gian Galeazzo, whom he allegedly poisoned when the political constellation was the most propitious for seizing the throne of Milan. To him and his astrological excess is dedicated the last chapter of the book. It deals with Ludovico’s “symbiotic relationship” with the Milan astrologer Ambrogio Varesi da Rosate (p. 206). He entrusted Varesi with planning marriages and establishing the most apt moment for every kind of event, including diplomatic meetings, the ratification of alliances, and military undertakings. He constantly resorted to elections (i.e., the astrological determination of the proper time to initiate actions) and interrogations (i.e., the casting of a chart to answer special questions, such as predicting the death of enemies), attracting the scorn of contemporaries and, later, of the famous Lombard astrologer, mathematician, and physician Girolamo Cardano. Stars were deemed to influence events, that is, to incline toward them without necessity. Hence, an excessive trust in elections and interrogations, dealing with particular effects, was seen as superstitious, since these were “less certain than other astrological practices” (p. 185). As Azzolini observes, the use of astrology increased in times of crisis and uncertainty. Ludovico himself eventually paid the fee of his own machinations and hazardous decisions. His support of France’s involvement in the Italian wars would result in the loss of his own duchy and the beginning of foreign domination in the peninsula.

Azzolini’s reflections on the Renaissance education in astrology and her reconstruction of the astrological background and theoretical preparation of Renaissance astrologers is rich in precious information for historians of science. Since Milanese court astrologers where often educated at the University of Pavia or taught there, she looks at that institution in order to gain information about their theoretical preparation. Yet, as the statutes are no longer extant, she gathers insights into astrological preparation at Pavia from indirect sources. First, Bologna’s 1405 statutes are a clue of the astronomical education imparted to the students at a university that served as a model for many others. Students in the arts and medicine started with spherical astronomy and planetary theory; in the third year, they were introduced to astrology through Alcabitius’s Introductorius ad iudicia astrorum and ps.-Ptolemy’s Centiloquium; in the fourth year, they faced medical astrology on the basis of William of England, Ptolemy’s Tetrabiblos, and Galen. Moreover, Azzolini derives evidence on the astrological preparation at Pavia from a manuscript owned by one of its most successful students, the Genoese physician-astrologer Giovanni Battista Boerio, physician-to-be of Henry VII and Henry VIII of England. The volume (British Library: MS Arundel 88) is a miscellanea that might be conveniently regarded as a sort of “specialized library” collecting astrological and medical-astrological texts, many of which had Arabic origins. Among other documents on Pavia, Azzolini considers the inventory of the books bequeathed to the library of Saint Thomas of Pavia by Antonio Bonareggi, illustrious professor at the local university (1418-47) and later court physician to Bianca Maria Visconti. Comparison of the titles appearing in such inventory and those included in Boerio’s collection leads Azzolini to the conclusion that the corpus astrologicum familiar to Pavia scholars was marked by a strong presence of Arabic works. It must have included such summaries as Haly Abenragel’s De iudiciis astrorum and such shorter texts as Messahalla’s De revolutionibus annorum mundi  and Zael’s De interrogationibus (p. 47). Azzolini tends to distinguish between astronomical sources, dealing with celestial motions and “propaedeutic and subservient to astrology,” and those properly dealing with astrology (p. 26). Given this premise, she looks for a corpus astrologicum clearly distinguished from the corpus astronomicum, and also from the corpus medico-astrologicum (pp. 47-48). Although disciplinary borders at late medieval universities might have been less neat than that, nonetheless these distinctions prove useful, in Azzolinis’s work, as heuristic tools for historical investigation.

Astrology, Azzolini explains in the theoretical introduction of chapter 1, was “used to predict events but would never offer certainty,” therefore it was never overtly deterministic (p. 58). It was a conjectural art and, as such, it was akin to medicine. While the computation of astrological charts required mathematical accuracy and astronomical skill, their interpretation left to the astrologer a large degree of freedom (p. 107). Prudent practitioners were able to find the right balance “between the rigor of professional expertise and the necessity to please one’s client or patron” (p. 111). How unwise could be an astrologer predicting the violent death of a tyrant is shown by episodes connected with Galeazzo Maria Sforza. Historical sources report that he convicted a priest to starve to death for foretelling him a short reign (p. 108). Additionally, Azzolini discusses documents about Galeazzo’s vexations against astrologers in Ferrara and Bologna, for casting negative predictions concerning him and his state (pp. 130-132). Yet, despite the risky and opportunistic aspects of their profession, Azzolini claims, astrologers were not “fraudulent” but, “on the whole, they operated with intellectual honesty and professional integrity,” given the restraints of their discipline (p. 63). To reinforce this perspective, she resorts to Grafton’s parallel between Renaissance astrology and present-day economics, based on consideration of the fact that both are “conjectural sciences” (p. 125). This comparison, repeated in several places (p. 63, 117, and 125), is not aimed at enhancing astrology or, even less, criticizing modern economics. Azzolini’s point is that Renaissance astrology was not intrinsically irrational, but, rather, it followed a rationality similar to those of Renaissance medicine and of present-day economics. Accordingly, Galeazzo “was not a fool,” when he asked the astrologer Annius of Viterbo, in 1475, to establish by means of astrology whether his enemy, the King of Naples Ferrante of Aragon, would soon die. Azzolini indulgently asserts that he just made use of “astrological intelligence” (p. 126). She often introduces such key expressions with an economical-political flavor: she talks about the “early modern predictive market” to stress the fact that astrological advice was in competition with other predictive sciences, and calls “astrological intelligence” the acquisition of astrological information by Renaissance rulers (pp. 66, 71, 126). Similarly, she treats astrological interrogations, such as predicting the death of a pope and his succession or the outcome of a battle, as an aspect of “the economy of information that characterized Renaissance diplomacy,” while annual prognostications can be seen as “the equivalent of economics’ annual projection of how the global market will behave” (pp. 118-119).

Use and abuse of astrology were both possible, as shown by the contrasting figures of Galeazzo and his brother Ludovico. The former used to gather advice from different astrologers. He interrogated them without informing them that others had been consulted on the same subject. In this manner, Galeazzo applied “quality control” and “approached astrological intelligence as a wise statesman would, namely with caution” (pp. 116-117). By contrast, Ludovico was rather incautious. His concerns about timing and the determination of every event per ponto d’astrologia were obsessive, as emerges from Azzolini’s detailed reconstruction. What’s more, he relied almost exclusively on the computations of a single advisor, Varesi da Rosate. Only in extremis, in the last days of his reign, when the French army besieged Milan, Ludovico’s trust in Varesi was shaken. At that point, he resorted to other astrologers’ counsel and broke the privileged relationship with him. Eventually, the fall of Ludovico brought disgrace also to his astrologer, who was captured, while he was fleeing from Milan. Varesi’s fief and possessions were withdrawn from him, and he was accused of the murder of Gian Galeazzo. Considering the preeminence that he had gained as an astrological advisor, many contemporaries saw in him the person responsible for the duke’s fall (p. 23). Azzolini’s analyses strengthen this viewpoint by stressing Ludovico’s morbid relationship with the astrologer and his excessive trust in the application of astrology to politics, diplomacy, and war (p. 21). Still, he was not unique in the Italian panorama and Azzolini calls for more comparative studies on this issue. She mentions as an example the fact that, according to Renaissance historians, the Venetians chose astrologically the day for the battle of Fornovo (July 6, 1495), in which they defeated the troops of the French invader, Charles VIII. In my opinion, the political relevance of astrology is even more vividly witnessed by Galeazzo’s reaction to the dissemination of astrological rumors concerning his person. In a letter written in 1474 to his ambassador in Ferrara, he lamented that social instability might result from the circulation of negative prognostications. “‘You know how serious things become when evil opinion spreads among the populace about some looming calamity, as it is often done by daring and vain astrologers.... Serious and honest people pay little attention to this type of prognostication; the populace, however, listens to them and waits in suspense, often giving rise to ideas that create chaos in those states and principalities. It is our opinion that His Holiness [i.e., the pope] should excommunicate all those astrologers and mathematicians who will have the presumption, in their prognostications, to name or specify a prince or lord ... but that it is allowed to them only to express universal predictions because the particular ones can throw up chaos and are dangerous, and religion and the Catholic faith forbid this type of superstition’” (p. 129). Thus, beyond the intrigues of palace, the personal ambitions of the rulers and the complex relationships among Renaissance dynasties, also the political role of the masses could be affected and guided by astrology. As Azzolini remarks, “Machiavellian political expediency took many forms in the Renaissance and spreading rumors was certainly one of them” (p. 134). Of course, the power of astrology did not lie in correctly predicting celestial influences, but rather in people’s belief in the reliability of such predictions. Azzolini’s study offers a suggestive introduction to that Renaissance world, to an epoch when the stars still shaped people’s lives and determined their fates.

In summary, not only is this book highly informative concerning the intellectual dimension of Renaissance astrology, but it also demonstrates how intellectual history can serve social and political history (e.g., family history and diplomatic history) and, vice versa, how the history of scientific disciplines might complement traditional history opening up new perspectives. Azzolini’s interdisciplinary research is firmly rooted in a thorough investigation of primary sources related to the vicissitudes of Renaissance Milan that have so far escaped historical attention. On the basis of astrological and medical manuscripts, letters and dedications to protectors, astrological charts and prognostics, and medical reports, Azzolini recounts the history of the Italian Quattrocento from an original viewpoint, namely, that of a dynasty, for which the private and the public spheres could not be kept apart, and its interactions with astrologers. This innovative use of sources permits her to overcome the difficulty to investigate scientific practices of the past. Her presentation of the everyday activity of forgotten practitioners and their patrons achieves an amazing degree of detail, and shall serve as a model for further comparative studies on early modern scientific culture.

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Citation: Pietro Daniel Omodeo. Review of Azzolini, Monica, The Duke and the Stars: Astrology and Politics in Renaissance Milan. H-PhysicalSciences, H-Net Reviews. December, 2013. URL:

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